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Biomolecules · Question 14

JEE Main 2026 (Online) 28th January Morning ShiftMCQMedium📈 Topic in 26% papers+4−1
1

In the given pentapeptide, find out an essential amino acid (Y) and the sequence present in the pentapeptide : [figure] Choose the correct answer from the options given below :

  1. arrayll(Y) & (Sequence) \ Serine & Thr-Ser-Asp-Ala-Gly array
  2. arrayll(Y) & (Sequence) \ Serine & Ser-Asp-Thr-Ala-Gly array
  3. arrayll(Y) & (Sequence) \ Threonine & Ser-Thr-Asp-Gly-Ala array
  4. arrayll(Y) & (Sequence) \ Threonine & Thr-Ser-Asp-Gly-Ala array

Answer

(4) arrayll(Y) & (Sequence) \ Threonine & Thr-Ser-Asp-Gly-Ala array

Solution

A peptide is written from the N-terminal (free -NH2) end to the C-terminal (free –COOH) end. Side chains on the α-carbons, from left to right:

1st: -CH(OH)CH3 Threonine (Thr)

2nd: -CH2OH Serine (Ser)

3rd: -CH2COOH Aspartic acid (Asp)

4th: –H Glycine (Gly)

5th: -CH3 Alanine (Ala)

Sequence: Thr-Ser-Asp-Gly-Ala

As per NCERT, threonine is an essential amino acid (it cannot be synthesised in the body), whereas serine, aspartic acid, glycine and alanine are non-essential.

Y = Threonine

Answer: (4)

JEE Main 2026 (Online) 28th January Morning Shift

Keep practising — Biomolecules

2

Structures of four disaccharides are given below. Among the given disaccharides, the non-reducing sugar is :

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2026 (Online) 28th January Evening Shift
3

The number of possible tripeptides formed involving alanine (ala), glycine (gly) and valine (val), where no amino acid has been used more than once is:

  1. 8
  2. 3
  3. 4
  4. 6
JEE Main 2026 (Online) 24th January Evening Shift
4

From the given following (A to D) cyclic structures, those which will not react with Tollens' reagent are: [figure]

  1. A and D
  2. A and B
  3. B and D
  4. B and C
JEE Main 2026 (Online) 23rd January Morning Shift
5

Both human DNA and RNA are chiral molecules. The chirality in DNA and RNA arises due to the presence of

  1. L-sugar component
  2. D-sugar component
  3. Chiral phosphate unit
  4. Base unit
JEE Main 2026 (Online) 23rd January Evening Shift
6

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Both Statement I and Statement II are false
  2. Both Statement I and Statement II are true
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true
JEE Main 2026 (Online) 22nd January Morning Shift
7

Match List-I with List-II. Choose the correct answer from the options given below :

  1. A-IV, B-III, C-II, D-I
  2. A-I, B-III, C-IV, D-II
  3. A-III, B-I, C-IV, D-II
  4. A-IV, B-I, C-II, D-III
JEE Main 2026 (Online) 22nd January Evening Shift
8

Identify the correct statements. Choose the correct answer from the options given below :

  1. C and D Only
  2. A and D Only
  3. C and E Only
  4. B and E Only
JEE Main 2026 (Online) 21st January Morning Shift
9

The correct statements are : Choose the correct answer from the options given below :

  1. A, B and D Only
  2. A, C and D Only
  3. B and C Only
  4. A and B Only
JEE Main 2026 (Online) 21st January Evening Shift
10

[figure] Choose the correct option for structures of A and B, respectively

  1. [figure] and [figure]
  2. [figure] and [figure]
  3. [figure] and [figure]
  4. [figure] and [figure]
JEE Main 2025 (Online) 8th April Evening Shift
11

Given below are two statements: In the light of the above statements, choose the correct answer from the options given below

  1. Both Statement I and Statement II are false
  2. Statement I is false but Statement II is true
  3. Both Statement I and Statement II are true
  4. Statement I is true but Statement II is false
JEE Main 2025 (Online) 7th April Morning Shift

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